The daily average number of COVID-19 cases and positivity rate ticked up over the Christmas and New Year’s holidays, according to the latest data from the state Department of Health.

DOH on Wednesday reported the state’s seven-day average of new COVID-19 cases increased to 177 compared with 156 reported Dec. 28. The state’s average positivity rate — or percentage of tests reported that are positive — rose to 7.9% compared with 7.1% the previous week.

Hospitalizations of COVID-19 patients also climbed, with the daily average of COVID-19 patients per day for the past week increasing to 81 compared with 60 from Dec. 15-21.

All eyes are on a new omicron subvariant, XBB.1.5, which rose to dominance over the holidays, and now makes up 40.5% of variants circulating in the U.S.

XBB.1.5, which some scientists have nicknamed “Kraken,” is a descendent of XBB —a recombinant of two different BA.2 sublineages that fueled rises in parts of Asia, including Singapore. XBB.1.5 was not listed in Hawaii’s Dec. 20 variant report.

Dr. Eric Topol, professor of molecular medicine at Scripps Research, warned as early as Dec. 23 that XBB.1.5 was on a growth spurt in the U.S.

He said XBB appears to have evolved to XBB.1.5 in New York state, with three mutations of note coinciding with the beginning of a rise in hospitalizations there and that “of all the variants in the current mix, XBB.1.5 has the most growth advantage vs. BA.5.”

The World Health Organization’s COVID-19 technical lead Maria Van Kerkhove said Wednesday that XBB.1.5 has been detected in 29 countries, so far, and possibly more.

She said WHO was concerned about its growth advantage, in particular, in some parts of Europe and in the Northeast in the U.S., where XBB.1.5 has rapidly replaced other circulating variants, but has no data on severity yet.

Last Friday the Centers for Disease Control and Prevention released its Nowcast model showing that XBB.1.5 makes up 40.5%, while BQ.1.1 makes up about 27% and BQ.1 makes up 18.3% of new COVID-19 infections in the U.S.

Omicron subvariant BA.5, which is targeted by the new bivalent booster formula, only makes up 3.7% of variants circulating in the U.S.

Dr. Ashish Jha, White House COVID-19 response coordinator, addressed the public Wednesday about XBB.1.5 in a Twitter thread.

“Over the holidays, you may have heard about omicron XBB.1.5,” said Jha in the thread. “It went from 4% of sequences to 40% in just a few weeks. That’s a stunning increase.”

Jha wrote that XBB.1.5 is likely more immune evasive than other omicron variants, and that it may be more inherently contagious because it binds more tightly to the human ACE receptor. However, he said it remains unknown if it is more dangerous or how well COVID-19 vaccines neutralize XBB.1.5.

“If you had an infection before July OR your last vaccine was before bivalent update in September your protection against XBB.1.5 infection is probably not that great,” he wrote. “We will soon have more data on how well vaccines neutralize XBB.1.5.”

The bivalent booster uptake in Hawaii — though better than the U.S. overall — has slowed and hovers at just below a quarter of the state’s eligible population.

As of Wednesday the Health Department reported a total of 261,272 residents, or 23.4% of the state’s eligible population, have received the bivalent booster.

DOH also reported four more deaths, bringing the state’s COVID-19 death toll to 1,765.